Peroxy dicarbonates



patented Aug. 8, 1950 UNITED STATES PATENT OFFICE PEROXY DICA tBONATEs; .William E. Bissinger, Akrom iohimassignor to Pittsburgh Plate Glass Gompany,-Allegheny County, Pa., a corporatiorrof Pennsylvania No Drawing. Application September. 10, 1946, Serial No. 696,039 1 This invention relates to a'novel group of compounds and methods of preparing such com-v pounds and to novel methods of polymerization involving use of such compounds as catalysts.

In accordance with the present invention a novel class of compounds which are esters of ni-troaliphatic alcohols and the theoretical peroxy vdicarbonic acid and which has the formula has been provided. These compounds, unlike many peroxy dicarbonates, are stable at room temperature but yield oxygen upon heating. They may be used effectively as polymerization catalysts to promote polymerization of polymerizable unsaturated compounds which polymerize by peroxide catalysts. The new peroxy 'dicarbonates are more stable than the corresponding compounds prepared from the corresponding alcohols having no nitro. groups.

The new group of compounds areunderstood to have the structure ethyl alcohol, etc.

The above new peroxy dicarbonates may be prepared from the corresponding haloformates of the nitro alcohols. These novel haloformates are prepared by reaction of phosgene with the nitroalc'ohol preferably ata temperature some- 'what below room temperature, usually to 15 C. The haloformatesv thus obtained, particularly those formed from liquid alcohols are usually liquids which are soluble in usual organic isolvents such as acetone, benzene; xylene, toluene, chloroform, ethanol, methanol, etc. They "decompose on heating andreact with alkaliesto form the corresponding carbonates.

The herein contemplated peroxy dicarbonates 5 Claims. (oijiatoaiss ;may. be prepared by reaction of the chloroformates of the nitro alcohols with hydrogen peroxide or an alkali metal peroxide such as sodium peroxide. This reaction may beeffected simply by mixing a solution -or slurry of the peroxide with the haloformate at a relatively low temperature preferably below room temperature and usually at about 0 to ;15 G. Since the reaction, is exothermic, cooling generally is required to prevent an undesirable temperature rise during the process.

A preferred method of reacting the nitro alkyl ,chloroformate with a peroxide involves the preliminary preparation of a slurry of sodium peroxide by reacting aqueous hydrogen peroxide with a solution of caustic soda. When this reaction is conducted in the presence of a stirring device a very finely precipitated sodium peroxide is formed which is subsequently added gradually to the nitro alkyl chloroformate with cooling and agitation. The nitro alkyl peroxy dicarbonate is then separated by filtration or by other suitable means.

,The peroxy dicarbonates herein disclosed may fb'e'used as bleaching agents or for other purposes'as a convenient source of active oxygen. They are useful as catalysts for the polymerization. of unsaturated polynierizable compounds which. contain one or more of the polymerizable groupsCH2=C=,' CHEC,

o-o=o-o- Al "it etcf'lSuch compounds include methyl methacrylate, methyl acrylate, styrene, maleic or fumaric esters of ethylene glycol or polyethylene glycol, .vinyl acetate, allyl or other unsaturated alcohol esters such as listed in U. S. Patent 2,403,112, etc. The temperatures of polymerization required will vary with the quantity of peroxide used andwith the length of the curing period. For. example, satisfactory hard castings may be obtained by-heating methyl methacrylate with OJ-percent of the peroxide for 48 hours at 45 C. to produce castings having substantially less color after exposure to accelerated Weathering conditions than the same composition when polymerized with an equal amount of benzoyl peroxide' Generally,fcasting, impregnating, and surface coating methods may be practiced with the new nitroalkyl peroxy dicarbonates in the same manner that those skilled in the art use benzoyl peroxide. Further details of the preparation and use of the new compounds are set forth in the following examples:

Example I A mixture of one part of 2-nitro-2-methylpropyl chloroformate was prepared by refluxing a dioxane solution containing 1.5 mols of liquid phosgene and 0.7 mol of the nitro alcohol at a temperature of 5 to C. for several hours in a system provided with a reflux condenser capable of condensing phosgene and of permitting escape 11 1.4448. It is a powerful lachrymator and is soluble in organic solvents such as acetone, ethyl alcohol.

9. 1 grams of the resulting 2-nitro-2 methylpro- "pyl-chloroformate was placed in a flask equipped withan agitator and was stirred at a temperature i t gu carbon df minus' 9 0. During the stirring, a solution which-had been" formed by mixing 3.3 gramsof 2'8 percent by weight hydrogen peroxide, 4.4 -grams of 50 percent byweight NaOH in milliliters of-wa'ter,"was added'to the *chloroforznate while the temperature of themi'xture was maint'akiried '*at'-2 to 7 C. A bluish colored solid was rer'mea, After-stirring for one hour the mixture was 'filtered'and the solid dissolved in absolute ethyl alcohol and recrystallized by addition of water to the alcohol solution. This solid which is the 'peroxy dicarbonate of the corresponding nitro alcohol having the structure melts at 98.5-89.5 C. with decomposition and is soluble in "organic "solvents s'uchas acetone, ethyl al'cohol and xylene. It was stable 'at30 for over "2Q days. I Inhibitor-free methyl *methacry'latecontaining (Ll i percent by weight "of this peroxy 'dicarbonate pelynierined 'to' a hard polymer when heated at C. for 72 hours.

Example II 56% NaOH, 13.5 grams of 28% hydrogen peroxide and'sufli'ci'ent water to make a total volume of 60 milliliters while maintaining the temperature of'the'mixture at 2 to 4 C. The mixture became thick. After 20 minutes of stirring, the mixture was extracted with ether and the ether extract evaporated to remove the ether. The resulting product is 2-nitrobutyl peroxy dicarbonate which has the structure CHa-CH2(EH-CHrO-C-OOGOOHr-CEL-CHz-OH N03 0 O NO:

This product melted at 48 to 495 C. and decomposed at 94 C. with evolution of gas.

This product efiectively catalyzes polymerization of methyl methacrylate when used in the concentration and at the temperature set forth in Example I.

The above process may be used for the production of the solid peroxy di'carbonate of 2- nitro-2-methyl-l-phenyl-l-propanol by use of this alcohol in lieu of -2-nitrobutyl alcohol. This product has properties similar to those of the above.

Peroxy dicarbonates of various other nitroalcohols including Z-m'troethanol, l-nitro-3- peh'terie-Z-ol, 5-nitro-2-heptene -4-ol, 2-nitro propanol, 2-nitro 3 methyl butanol, nitropentanols such as Z-nitro-n-pentanol, 3 nitropentanol, or other monohydroxy nitro alcohols preferably containing the structure where Band B are aliphatic hydrocarbon radicals linked to the "indicated carbon atoms These peroxydicarbonates are generally solids "and liberate oxygen on heating. In the formulae above indicated the nitro groups'ar'e "indicated generally as being linked to a carbon atom without attempt to indicate the atomic relationship of the atoms of the monovalent nitro group. Modern theory tends to supportitne viewpoint that nitro compounds have the structure at least one of the oxygen atoms being linked to the nitrogen atom by a coordinate linkage or bond. However, applicant does not desire to be bound by any theory respecting the exact structure of'the nitro radical.

Although the present invention has been described with reference to thespec'ific details of certain embodiments thereof, it is not intended that such details shall be regarded as limitations upon the scope of the invention except insofar asincluded in the accompanying claims.

'Iclaim;

1. His -'2 nitro-'n-butyl) peroxydicarbonate ens-cH2-cH-c112-o-o-o-o-o-o-oEo-On-o112-0113 N02 I l N02 H 2. Bis (2 --nitro -2-methyl-n-propyl) peroxydicarbonate 3. methodofpreparing a peroxy dicarbonate of a nitro aliphatic monohydric alcohol having the' formula R'NO2 H which comprises reacting a chloroformate of the nitro aliphatic alcohol with a peroxide of the "group consisting of hydrogen peroxide and a1- 'kali 'r'netal peroxides. 4

4. The process 'of'claim '3 wherein the peroxide isfsodium peroxide.

5. A diester'of a nitroaliphatic monohydric a1- ooh"ol l'i'a-v'ing the fo'rmula Ii -N01 REFERENCES CITED The following references are of record in the file of this patent: 10

UNITED STATES PATENTS Number Name Date Pollack Oct. 24, 1944 Strain Feb. 27, 1945 Strain May 1, 1945 Strain -1 Apr. 2, 1946 Stevens Feb. 18, 1947 

5. A DIESTER OF A NITROLIPHATIC MONOHYDRIC ALCHOL HAVING THE FORMULA 